Public Domain. Emma Cumming.

Public Domain can also be known as Trademarks, which is an instinctive sign or indicator used by an individual.

Definition of Public Domain:

A group of computers and devices on a network that are administered as a unit with common rules and procedures. Within the Internet, domains are defined by the IP address. All devices sharing a common part of the IP address are said to be in the same domain. In database technology, domain refers to the description of an attribute's allowed values. The physical description is a set of values the attribute can have, and the semantic, or logical, description is the meaning of the attribute.

Source from http://www.webopedia.com/TERM/d/domain.html

Public Domain is 'public property' it is free for anyone to use for any reason. They have the right to copy but sometimes Public Domain is contrasted by the works of the restrictions of Copyright.